This invention relates to a method and apparatus for carrying out the dynamic balancing of bodies rotating at any speed; the invention is particularly suitable for automatic dynamic balancing of centrifuges, turbine rotors, wheels and discs.
As it is known, bodies meant to rotate, particularly at high speeds, must not display mass unbalances which would cause, during rotation and operation, vibrations which are risky and dangerous to the physical integrity of the body and to the machine on which it is mounted. In order to achieve the uniformity of structure and the tolerances of mass necessary in order to avoid the above mentioned vibrations, the bodies in discussion should therefore be worked and manufactured with extremely high precision, which often is technologically difficult.
It has therefore been necessary, once the body has been manufactured, to successively utilize static or dynamic balancing technologies in order to modify the body mass at such points and to such extent to eliminate the cause of said vibrations.
According to a previous invention by the same Assignee (U.S. Pat. No. 4,096,988) a method and apparatus are provided by means of which balancing may be carried out during operating conditions, i.e. while the body is rotating, that is without the necessity for it to be stopped, in contrast with the usually long and costly balancing procedures. According to the prior invention, which refers particularly to the balancing of rotating bodies at high speeds which during rotation are subject to deformation, the means for carrying out the balancing may be formed by several operating members capable of removing from the rotating body, by means of fusion or sublimation, or by applying on it in predetermined positions, predetermined quantities of material. However, these means are placed in a fixed position with respect to the rotating body and come into operation in coincidence with action positions of the body and for such periods which, by means of addition or removal of material vary the mass of the rotating body in the amount determined to obtain the balance. By way of a non limiting example, it was suggested to use a laser as the operating member, which permitted the addition of energy even in a vacuum and reduced the time of intervention to extremely low values.
However, in the practical application of the above described method it became apparent that the necessary characteristics of the laser made it extremely expensive, and at any rate extremely difficult to find. Lasers commercially available have extremely short impulse durations, on the order of a nano-second or a pico-second, and therefore in order to obtain the desired effect the above described method of removal of material, that is of balancing, a laser with extremely high peak power, which is very expensive, would be necessary. Lasers of a lower price and capable of operating within parameters (periods in the order of the micro-seconds, energies in the order of tenths of Joules) suitable for carrying out the method do not exist.